1. Field of the Invention
The present invention relates to a throttle valve control device for an internal combustion engine for transmitting rotation of a motor depending on an input of an accelerator pedal to a valve shaft of a throttle valve for adjusting amount of intake air to an internal combustion engine through a gear train unit consisting of a sun gear, a ring gear of an inner teeth type and planetary gear mating to foregoing gears.
2. Description of the Prior Art
FIG. 16 to FIG. 19 illustrate prior arts which have been filed by the present applicant but not yet been laid open to public: FIG. 16 is a side view partially cut away the throttle valve device for an internal combustion engine, FIG. 17 is a sectional view of FIG. 16 along line Dxe2x80x94D, FIG. 18 is a front view of the valve housing and FIG. 19 is a front view of the ring gear. In FIG. 16, 1 is an internal combustion engine, 2 is a throttle valve, 3 is a valve housing of the throttle valve 2, 5 is a valve shaft being rotably provided in the value housing 3 a crossing an intake air passage 4, 6 is a valve body attached to the valve shaft 5, 7 is a intake pipe such as a manifold to connect the intake air passage 4 to unshown intake air hole, 8 is a motor such as DC brushless motor arranged with abutment to the throttle valve 2, 9 is a motor housing of the motor 8, 10 is a stator stored in the motor housing 9, 11 is a rotor being a counterpart of the stator 10, 12 is a out put shaft to which the rotor 11 is attached, 13 is a bearing rotatably supporting one end of the output shaft 9 at the motor housing 9, and 14 is a terminal which is connected to the coil of the stator 10 and assembled into the motor housing 9. According to arrangement of the motor 8 and the throttle valve 2 with mutual abutment thereof, rotation center of the output shaft 12 and that of the valve shaft are placed coaxially on a single straight line as shown by a chain with a single dot line and the other end of the output shaft 12 and an end of the valve shaft 5 are placed facing mutually with a gap, and the end face of the opening of the motor housing 9 formed annularly along periphery on the other side of the output shaft 12 and the end face of the opening of the valve housing 3 formed annularly along periphery of one side of the valve housing 3 are arranged to be butt jointed; in this arrangement with mutual abutment of the throttle value 2 and the motor 8, a gear train unit 16 is assembled into an inner space 15 which is hermetically sealed by the valve housing 3 and the motor housing 9; the gear train unit 16 consists of a sun gear 17, a ring gear of inner teeth type and a planetary gear 19 mating with foregoing gears; the sun gear 17 is arranged to rotate together with the output shaft 12 of the motor 8 and the rotation center of the sun gear and that of the value shaft 5 are arranged coaxially facing each other; the ring gear 18 is provided with a center body 181 having a rigidity, a teeth portion 182 made of a synthetic resin being die molded with respect to the center body 181 and rotation detent portions 183 made of a synthetic resin die molded with respect to the center body those of which are integrated to a single body; the teeth portion 182 of the ring gear 18 is arranged coaxially with and around the sun gear 17, and the center hole portion 184 of the ring gear 18 is arranged coaxially with and rotatably to the output shaft 12 through the bearing 20; the peripheral surface of the ring gear 18 on the side of the teeth portion 182 contacts with the inner peripheral surface of the value housing 3 and that of the motor housing 9 those of which form the inner space, and the ring gear 18 is fixed to the valve housing 3 and the motor housing 9; the rotation center of the planetary gear 19 is coupled to the supporting member 21 fixed to an end of the valve shaft 5 so as to be rotatable together with the valve shaft 5 through the supporting rod 22; in this way, after the gear train unit 16 is assembled into the inner space 15, the valve housing 3 and the motor housing 9 are mutually connected by means of unshown securing means such as a bolt; 23 is a spring such that the valve body 6 exerts a force on supporting member 21 for bringing back the intake air passage to the position of an intermediate opening; 24 is a control unit for supplying electric power to the terminal 14 of the motor 2, 25 is a accelerator pedal, and 26 is accelerator sensor for outputting electrical signal obtained through conversion of detection value of the input of the accelerator pedal 25 to the control unit 24.
Description is subsequently given of the operation of the throttle value control unit. When the accelerator pedal 25 is operated, the accelerator sensor 26 detecting the input of the accelerator pedal outputs an electric signal to the control unit 24 and the control unit 24 supplies an electric power corresponding to the electric signal from the accelerator sensor to the terminal 14 of the motor 8; the stator 10 produces a rotating magnetic field depending on the electric current flowing through the coil of the stator 10; the output shaft 12 rotates due to the attraction and repulsion caused by the rotating magnetic field produced by the stator 10 and the magnetic field in possession of the rotor 11, and in turn the sun gear 17 rotates together with the output shaft 12; and then the planetary gear 19 performs a revolution centering on the sun gear 17 and a rotation centering on the supporting rod 22; and by virtue of the revolution of the planetary gear the valve shaft 5 rotates through the supporting rod 21, and by the rotation of the valve body 6, sectional area of the intake air passage is adjusted. Thus, the gear train unit 16 consisting of the sun gear 17, the ring gear 18 and the planetary gear 19 transmit the rotation of the motor 2 depending on the input of the accelerator pedal 25 to the valve shaft 5 of the valve 2 for adjusting the amount of intake air to the internal combustion engine 1 through the supporting member 21.
In FIG. 17, the ring gear 18 comprises a plurality of rotation detent portions 183 and yet these detent portions 183 are provided by a number which is required in order to satisfy the strength at an arbitrary positions and are stored in the valve housing 3 with engagement to the valve housing and thereby preventing the ring gear 18 from rotation along peripheral direction. In FIG. 18, the valve housing 3 is formed of groove shaped engagement portions 3a on the inner peripheral surface which forms the inner space 15 as shown by FIG. 16 and these engagement portions 3a are arranged at three positions of P11xcx9cP13 out of four positions of P11xcx9cP14 which are intersecting points of the inner peripheral surface with two straight lines of L12 and L13 which intersect perpendicularly; the valve housing is provided with, outwardly from the center and concentric circularly, a through hole 36 for valve shaft, a recessed portion 3c for receiving the bearing, a spring guide positioning portion 3d, and a recessed portion 3e for reception of the spring; outside the recessed portion 3e for reception of spring, a supporting member clearance groove 3f and a spring guide stopper clearance groove 3g are arranged; on outer peripheral surface of the valve housing 3, an air hole 3h penetrating between outside and inside thereof is provided; when the unit consisting of the throttle valve 2 and the motor 8 is installed to an internal combustion engine 1, the air hole 3h is directed toward ground and thus water collected by dew condensation in the inner space 15 is drained out through the air hole 3h. 
In FIG. 19, a plurality of rotation detent portions 183 project to outside along radial directions from the outer peripheral surface of the ring gear at three positions of P1xcx9cP3 out of four positions of P1, P2, P3, P4 defined by intersections of the peripheral surface with two straight lines L12, L13 intersecting perpendicularly each other. When the ring gear 18 is inserted to the valve housing 3 to engage with it, because the rotation detent portions 183 is inserted to the engagement portions 3a separately, the ring gear 18 is placed in the valve housing 3 so as not to rotate as shown by FIG. 17.
In the aforementioned conventional throttle valve control device, since the rotation detent portions 183 are not arranged along the peripheral direction with equidistance, there may the be a possibility of the circularity of the teeth portion 182 formed inside of a deterioration of the center body 181 because of a contraction of the synthetic resin after the formation of the synthetic resin. Result of measurement of the circularity is shown by the dotted line L11 in FIG. 8. According to this dotted line L11, as to the pitch circle of the teeth portion 182, generation of deformation of 0.20 mm from xe2x88x920.15 mm to +0.05 mm may be acknowledged.
The object of the present invention is to provide a throttle valve control device for an internal combustion engine which is provided with a ring gear with an improved accuracy of circularity of that gear.
A throttle valve control device for an internal combustion engine according to the invention of claim 1 comprises a gear train unit which consists of a sun gear for transmitting the rotation of an output shaft to a valve shaft of a throttle valve, a ring gear of an inner teeth type and a planetary gear mating to the sun gear and the ring gear and the sun gear, the ring gear and the planetary gear are arranged in a space formed by making a butt joint of a valve housing for the throttle valve for adjusting amount of intake air to the internal combustion engine and a motor housing of a motor for rotating the output shaft depending on an input of an accelerator pedal, wherein the ring gear comprises a center body having a rigidity, a teeth portion made of a synthetic resin being die molded with respect to said center body through a die, rotation detent portions for preventing said ring gear, which are stored in and fitted to at least either one of the valve housing or motor housing, from rotation along peripheral direction of the ring gear and contraction detent portion(s) of the teeth portion with respect to the center body, and the rotation detent portion(s) and the contraction detent portion(s) arranged along a peripheral direction of the ring gear with an equidistance.
In a throttle valve control device for an international combustion engine according to claim 2, a plurality of the rotation detent portion(s) as recited in claim 1 and a plurality of the contraction detent portion(s) as recited in claim 1 are provided.
In a throttle valve control device for an internal combustion engine according to claim 3, the contraction detent portion(s) as recited in claim 1 is (are) formed by a synthetic resin within a minimum size which is defined by a flowable synthetic resin into a molding die.
In a throttle valve control device for an internal combustion engine according to claim 4, the contraction detent portion or portion(s) as recited in claim 1 is(are) fixed to the center body.
In a throttle valve control device for an internal combustion engine according to claim 5, center body as recited in claim 1 is made of a metal.
In a throttle valve control device for an internal combustion engine according to claim 6, the center body as recited in claim 1 is formed by drawing.
In a throttle valve control device for an internal combustion engine according to claim 7, the center body and the teeth portion as recited in claim 1 are integrated to a single body by filling in and solidifying a molding material of the teeth portion after placing the center portion into a molding space of a molding die of the teeth portion.
In a throttle valve control device for an internal combustion engine according to claim 8, the sun gear as recited in claim 1 comprises a central hole portion for arranging the center body coaxially with the sun gear.
In a throttle valve control device for an internal combustion engine according to claim 9, the center body as recited in claim 1 comprises a peripheral wall which engages inscribably with both of an inner peripheral surface of the valve housing and an inner peripheral surface of the motor housing, those of which form the inner space.
In a throttle valve control device for an internal combustion engine according to claim 10, the center body as recited claim 1 comprises a connecting means of synthetic resin of the teeth portion.
In a throttle valve control device for an internal combustion engine according to claim 11, the connecting means of synthetic resin as recited in claim 10 is a through hole.
In a throttle valve control device for an internal combustion engine according to claim 12, the teeth portion as recited in claim 8 comprises an engagement portion which contacts with the motor housing on the outer peripheral surface of the central hole of the center body.